Add Wikipedia fallback so every game has cover art

libretro-thumbnails stops at the retro consoles, leaving the ten Xbox 360
titles blank. English Wikipedia carries a cover on essentially every
notable game article and needs no account, so it now runs as a second pass
for anything libretro cannot match.

Correcting an earlier claim in this repo: libretro does publish a
"Microsoft - Xbox 360" set. I had reported it as absent after checking only
my own hardcoded system map, not the actual catalogue of 123 sets. The set
turns out to hold about a dozen entries, none of them ours, so the
conclusion held but the reason given was wrong. It is now mapped and
searched anyway, in case it fills out later.

The cover filename is read from the article's infobox rather than inferred
from file names: filtering names for "box" also matches
"Xbox-360-Pro-wController.png". Two details that cost a round each:

  * the infobox writes the field both bare ("Halo 3 final boxshot.JPG") and
    prefixed ("File:Lost-Planet-New.jpg"), so any prefix is stripped before
    exactly one is added back
  * the API returns 429 under an unthrottled loop, so calls are spaced one
    second apart, retried with a longer backoff, and cached to disk

Coverage is now 105/105 — 93 from libretro, 12 from Wikipedia.

Two rows took art of the right game but the wrong platform, because their
system field looks wrong in the source data: a Game Boy "Donkey Kong
Country 2" and a DS "Donkey Kong Country Returns". Noted in the README
rather than silently corrected.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -77,21 +77,33 @@ cd backend  && dotnet build      # 0 warnings expected
 
 ### Cover art
 
-`tools/cover-art/fetch_art.py` fills in box art from
-[libretro-thumbnails](https://thumbnails.libretro.com), matching on title +
-system and pushing each image through the app's own `POST /api/images`, so it
-gets the same validation and WebP re-encoding as a manual upload. Standard
-library only — no virtualenv needed.
+`tools/cover-art/fetch_art.py` fills in box art, pushing each image through the
+app's own `POST /api/images` so it gets the same validation and WebP re-encoding
+as a manual upload. Standard library only — no virtualenv, and neither source
+needs an account.
+
+It tries two sources in order:
+
+1. **[libretro-thumbnails](https://thumbnails.libretro.com)** — scanned retail
+   boxes, named to the No-Intro / Redump conventions. Best art where it has any,
+   but its coverage is the retro consoles. Its `Microsoft - Xbox 360` set exists
+   but holds about a dozen entries.
+2. **English Wikipedia** — a cover on essentially every notable game article,
+   which is what fills the Xbox 360 shelf. The exact filename is read from the
+   article's infobox rather than guessed from file names, since filtering names
+   for "box" also matches `Xbox-360-Pro-wController.png`. Calls are throttled to
+   one per second and cached; the API returns 429 if pushed harder.
 
 ```bash
 cd tools/cover-art
-python3 fetch_art.py --password '...' --dry-run   # report matches, change nothing
-python3 fetch_art.py --password '...'             # download and attach
-python3 fetch_art.py --password '...' --overwrite # also replace existing art
+python3 fetch_art.py --password '...' --dry-run      # report matches, change nothing
+python3 fetch_art.py --password '...'                # download and attach
+python3 fetch_art.py --password '...' --overwrite    # also replace existing art
+python3 fetch_art.py --password '...' --no-wikipedia # libretro only
 ```
 
-Always dry-run first; it prints every match with a similarity score and flags
-anything below 0.95 for eyeballing.
+Always dry-run first; it prints every match with a similarity score, marks the
+source (`W` for Wikipedia), and flags anything below 0.95 for eyeballing.
 
 Matching handles the gaps between a personal catalogue and a ROM-naming one:
 accents (`Pokemon` → `Pokémon`), roman numerals (our SNES `Final Fantasy 2` is
@@ -100,9 +112,13 @@ subtitles in either direction, and outright typos — `Brett Hull Hocky 95` find
 `Brett Hull Hockey 95`. A sequel guard stops `Donkey Kong Country 2` from
 silently taking `Donkey Kong Country`'s box.
 
-**Xbox 360 is not covered** — libretro has no thumbnail set for it, so those 10
-titles are reported as unsupported. They need a source such as IGDB, which
-requires a free Twitch developer client ID and secret.
+All 105 games currently have art: 93 from libretro, 12 from Wikipedia.
+
+Two rows got art of the right *game* but the wrong *platform*, because the
+platform in the source data looks wrong — a Game Boy "Donkey Kong Country 2"
+(never released on that system; the handheld sequels were *Donkey Kong Land*)
+and a DS "Donkey Kong Country Returns" (a Wii game, later *Returns 3D* on 3DS).
+Fix the system field and re-run with `--overwrite` to correct them.
 
 Art is publisher copyright. Fetching it for a private collection is ordinary
 practice for library software; redistributing it is a different question.